Tire Size Front 2.75-21 Rear 4.00-18

Does this mean the front tire is almost 3" high or wide? And what does the - 21 mean?

The rear 4.00 high or wide. And what does the 18 stand for.

In other words how do you read these measurment?

Edited April 9, 200620 yr by BillyT

BillyT,

2.75" Wide.

21" Rim size. (Inside diameter.)

4.00" Wide.

18" Rim size. (Inside diameter.)

Thanks for the info, but how do I get the outside diametre of the front and back tire?

Thanks

Hi,

why would you need it?

Why can't you measure the circumference of the wheel and tyre, or measure how far it travels on the ground for a complete revolution?

Why can't you measure the circumference of the wheel and tyre, or measure how far it travels on the ground for a complete revolution?

<{POST_SNAPBACK}>

And then divide by 3.14 or some kind of pie ??????????

Bloody hell,

my Maths teacher said it would come in usefull one day,thats what they use it for!

Guys not looking for the circumfrence just the outside diamter of the tire.

I do not have a bike at hand or I would measure it myself.

Can some one measure the diamtere of the front and back tire for me?????

Thanks

Michelin X11

Rear= 213 mm OD

Front= 221 mm OD

Thanks JTT

But still do not have the answer to my question.

I will ask it another way. If I were to cut a slot out on a piece of wood how long would it have to be to fit the rear tire through, then the same question for the front.

Again that would be the diameter of the tire mounted on then wheel.

Or twice the radius.

Any one got a tape measure

Edited April 10, 200620 yr by BillyT

Depending on tyre pressures.

FRONT APPOX 27 1/2"

REAR APPOX 26 1/2"

Sounds like some one is making a bike trailer?

the diameter of both tyres are the same because the front is a smaller profile from the back

my tyres are not new but both measure (approx) 28" diameter

so if you are making a bike trailer or similar then somewhere about 24" would be ok i would think as you obviously dont want to make it the same as the full diameter or you'll be sitting on the swingarm/fork legs..

hope this helps,